Hi Lily, don't worry, cause every pregnancy is different. As long as the baby is healthy, it is good enough. Your baby may have spurt growth in the 3rd trimester since you started eating well from 24th week. I have a colleague who gained very little weight, only can see tummy in 3rd trimester and only gain 12kg in total, but her baby is 4kg when she was induced at 40 weeks.
I eat normal except for the first trimester where I will go hungry suddenly and have to eat food fast. But I still put on alot of weight during the 2nd trimester. My friend's sister in-law says that she gained very little weight in the beginning, but during the 3rd trimester, she put on 1kg/week. So make me abit scared, since I already put on so much in the beginning. But I stay optimistic, tell myself that maybe because my tummy is elastic, so can gain more in the beginning, later will stabilise. Even if I have tremendous weight gain, I will try to lose the weight after birth, most important is baby is healthy and safe.